Practical Industrial Data Networks:Design, Installation and ...

Appendix B – Basic terminology 325Guard Band5 10 15Frequency kHzFigure B.11Broadband signalB.5 Narrowband vs widebandB.5.1B.5.2NarrowbandAlthough narrowband and wideband sound very much like baseband and broadband, theyhave absolutely nothing in common. Narrowband and wideband refer to the relativebandwidth of the channel.A narrowband system is simply a system with a relatively small bandwidth. Thefollowing systems can be classified as narrowband:• Links designed to connect teletypes with a bandwidth of 300 Hz.• A plain old telephone system (POTS) with an available bandwidth of about3 kHz. With the aid of modems they can carry data at speeds up to 56 kbps.• BRI ISDN (2B+D) with two channels for voice or data, at 64 kbps each.• A T-1 channel with a bandwidth of between 64 kbps and 1.54 Mbps.WidebandThe following systems can be classified as wideband.• T-3 operating at 44.7 Mbps. It is equivalent to 28 T-1 circuits and cantransmit 672 conversations simultaneously over fiber optics or microwave.• ATM, carrying data, voice and video at speeds up to 13.22 Gbps.• Likewise SONET, an optical multiplexing interface for high-speed datatransmission, can operate up to 13.22 Gbps.• Cable TV (CATV), broadcasting local and satellite TV channels using500 MHz bandwidth.• Digital high-definition TV (HDTV), used for broadcasting TV at 6 MHzper channel.